Anisotropic dielectronic resonances from magnetic-dipole lines Yuri Ralchenko National Institute of Standards and Technology Gaithersburg, MD, USA ADAS Workshop, 2013 Supported in part by the Office of Fusion Energy Sciences, U.S. DoE

Analyzing 10,000-eV dielectronic resonances with 80-eV forbidden lines Yuri Ralchenko National Institute of Standards and Technology Gaithersburg, MD, USA ADAS Workshop, 2013 Supported in part by the Office of Fusion Energy Sciences, U.S. DoE

Yu. Ralchenko & J.D. Gillaspy Physical Review A 88, (2013)

Radiative recombination  Continuum Bound states Ion recombined

DR step 1: dielectronic capture  Continuum Bound states Resonant process!

Continuum Bound states Dielectronic capture + autoionization = no recombination DC and AI are direct and inverse

DR step 2: radiative stabilization  Continuum Bound states Stabilizing transition: Mostly x-rays

Dielectronic recombination in plasmas Z Z+1 … Maxwellian Electrons are present at all energies (Infinite) Series of transitions are to be accounted for

DR measurements on EBITs EBIT electron beam extracted ions Is ionization distribution the same inside and outside the trap?..NO! 1.Extract ions 2.Measure ionization distribution Beam energy time ERER ERER ERER Fast beam ramping DR energy generally does not coincide with the energy of max abundance

DR resonances with M-shell (n=3) ions LMN resonances: L electron into M, free electron into N 1s 2 2s 2 2p 6 3s 2 3p 6 3d n

Calculation of LMn DR strength: Ca-like 3d 2 W 54+ 2s 1/2  3d 2p 1/2  3d 2p 3/2  3d e  3d e  4l e  5l 2s 1/2  3d 2p 1/2  3d 2p 3/2  3d e  3d e  4l e  5l 1s 2 (2s2p) 8 3s 2 3p 6 3d + e  1s 2 (2s2p) 7 3s 2 3p 6 3d 2 nl Relativistic model potential + QED corrections (Flexible Atomic Code, Gu 2008) Relativistic model potential + QED corrections (Flexible Atomic Code, Gu 2008)

Strategy 1.Scan electron beam energy with a small step (a few eV) 2.When a beam hits a DR, ionization balance changes 3.Both the populations of all levels within an ion and the corresponding line intensities change as well 4.Measure line intensity ratios from neighbor ions and look for resonances 5.EUV lines: forbidden magnetic-dipole lines within the ground configuration A(E1) ~ s -1 A(M1) ~ s -1 I = N  A  E (intensity) Ionization potential Ca-like W 54+

Beam energy: 0.1 keV – 30 keV Beam resolution: ~50 eV Beam current: ≤ 150 mA Beam radius: ~30 μm Electron density: ~10 12 cm -3 Can produce > 60-times ionized atoms Ar, Kr, Xe, Sn, Ti, Sm, Gd, Dy, Er, Hf, Ta, W, Pt, Au, Bi,… NIST Electron Beam Ion Trap x10 Monoenergetic beam allows one to “touch” dielectronic resonances

Yu. Ralchenko et al, Phys. Rev. A 83, (2011) Almost all lines are M1 Good statistics Isolated lines Pair of lines: (a) within 3d in K-like W 55+ (b) within 3d 2 in Ca-like W 54+ EUV spectrum of W 47+ -W 56+ : M1 lines within 3d n ground configurations

[Ca]/[K]

[Ca]/[K]: THEORY: no DR Modeling: CR code NOMAD, atomic data from FAC

[Ca]/[K] THEORY: no DR

[Ca]/[K] THEORY: no DR isotropic DR Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~10,500 levels

[Ca]/[K] THEORY: no DR isotropic DR anisotropic DR atomic level degenerate magnetic sublevels J m=-J m=+J Impact beam electrons are monodirectional Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~10,500 levels

[Ca]/[K] THEORY: no DR isotropic DR anisotropic DR atomic level degenerate magnetic sublevels J m=-J m=+J Impact beam electrons are monodirectional Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~18,500 levels

[Ca]/[K] 2p 3/2  3d e  4l 2p 3/2  3d e  4l

One EBIT run, several ions… Ca n=4 Sc Ti

Where are the 10-keV photons?.. 2p 5 3s 2 3p 6 3d n+1 4l 2s 1/2 2p 1/2 2p 3/2 3s 3p 3d 4s 4p 4d 4f ~8keV ~9keV ~11keV

X-ray emission (Ge detector) 2p 5 3/2 -4l 2p 5 3/2 -3d 2p 5 3/2 -3s B and C: horizontal A: slant  n>0 transitions into the 2p 3/2 hole

Conclusions A new in situ method to measure multi-keV dielectronic resonances in 3d n ions using ratios of EUV magnetic-dipole lines First resolved measurements of LMN resonances in ~55-times ionized W CR modeling shows importance of anisotropic effects on ionization balance Isolated resonances allow determination of the beam width

Probability of dielectronic recombination Z Z+1 … dielectronic capture  A a autoionization A a radiative decay A r

Examples of dielectronic recombination & resonances A. Burgess, ApJ 139, 776 (1964) This work solved the ionization balance problem for solar corona Ar at NSTX, Bitter et al (2004) Dielectronic satellites are important for plasma diagnostics (e.g., He- and Li-like ions) BUT: DR for high-Z multi-electron ions is barely known! BUT: DR for high-Z multi-electron ions is barely known!

Why is DR analysis still important? With DRWithout DR NLTE-6 Code Comparison Workshop Example: NLTE-6 Code Comparison Workshop, 2009; Ar at cm -3

LMM resonances in Ti-like Ba 34+ McLaughlin et al, Phys. Rev. A 54, 2040 (1996) One of the first NIST EBIT papers

B. Blagojevic et al, Rev. Sci. Instrum., 76, (2005). Grazing incidence diffraction grating Resolving power R=350 Optimized for weak signals EUV spectrometer